When a storage apparatus which is to be used in a computer system is configured, a storage apparatus with a built-in ASIC (Application Specific Integrated Circuit) as hardware designed specifically for a storage apparatus has been proposed (called ASIC storage hereinbelow) (see PTL1 in particular). In the ASIC storage disclosed in PTL1, a configuration is adopted in which, if an I/O (Input/Output) request is received, a CPU (Central Processing Unit) executes processing of the I/O request (hereinafter called I/O processing), the ASIC executes parity computation, authentication code computation, and compression computation, and the like, the CPU processes control information which is used in the I/O processing, the ASIC processes user data which is used in the parity computation and so on, and the CPU and ASIC are in charge of different processing.
In cases where ASIC storage is configured, a costly ASIC must be built in as hardware designed specifically for a storage apparatus. For this reason, in recent years, for the purpose of lowering overall system costs, the demand has increased for a storage apparatus which is configured without a built-in ASIC (hereinafter called ASIC-less storage). Here, the ASIC-less storage does not contain an ASIC and therefore I/O processing and computational processing such as parity computations are executed by the CPU, and hence the CPU processes control information which is used in the I/O processing and user data which is used in the parity computation and the like.